Some of projection type image display apparatuses such as liquid crystal projectors has, as a subdisplay on a back side portion of the apparatus besides a display unit that projects and displays an image onto a screen etc., a small liquid crystal display for displaying various types of information such as projected image information and a state of the apparatus.
For example, Japanese Patent Application Laid-open No. 2005-221898 (Patent Document 1) describes an apparatus: having a subscreen provided opposite a projection lens of a projector apparatus; and displaying the inputted image information to superimposedly display, on the image information, a message transmitted from a terminal apparatus.
Moreover, as a technique related to an apparatus having a subdisplay, for example, Japanese Patent Application Laid-open No. 2012-150082 (Patent Document 2) describes a vehicle navigation device including: a main display such as a liquid crystal display installed in the vicinity of a driver's seat and displaying a route guidance screen and a television screen; and a subdisplay arranged in the vicinity of a rear seat and displaying a route guidance screen, a screen of a television, a game, or the like, and discloses that so-called electronic paper may be used as the subdisplay.
Moreover, Japanese Patent Application Laid-open No. 2004-29801 (Patent Document 3) describes a technique of: using a display that utilizes a memory type reflective liquid crystal as a subdisplay of a personal computer; displaying, onto the subdisplay, fixed information not requiring frequent rewriting, a window to be inactive hiddenly on a main display of the personal computer, an image for enjoyment, and the like; and thereby enhancing efficiency of work such as editing by making effective use of a region of the main display.